Essentially, chromosomes are made up from DNA and so carry the genetic code that defines us as individuals.

Human DNA consists of 46 chromosomes, arranged in 23 different pairs.

Half of these chromosomes come from our mothers and half from our fathers.

Of the 23 pairs, one defines the sex of a baby. If a father passes on an ‘X’ chromosome then a child will be female, a ‘Y’ chromosome would result in a son.